An engine is known that has a first fuel injection valve for injecting fuel into a combustion chamber of the gasoline engine (in-cylinder injector) and a second fuel injection valve for injecting fuel into an intake manifold (intake manifold injector), and changes the fuel injection ratio between the in-cylinder injector and the intake manifold injector according to the engine speed or engine load.
In a low-pressure fuel system including the intake manifold injector (intake manifold injector and pipe), a feed pump is used to supply fuel to the intake manifold injector via a low-pressure-system delivery pipe, and the intake manifold injector injects the fuel into the intake manifold for each cylinder of the engine. In a high-pressure fuel system including the in-cylinder injector (in-cylinder injector and pipe), fuel supplied from the feed pump to a high-pressure fuel pump has its pressure increased by the high-pressure fuel pump and is supplied via a high-pressure delivery pipe to the in-cylinder injector, and the in-cylinder injector injects the high-pressure fuel into a combustion chamber for each cylinder of the engine. Here, the pressure of the fuel generated by the feed pump (feed pressure) is approximately 400 kPa, and the pressure of the fuel generated by the high-pressure fuel pump operated by a cam provided to the driveshaft coupled to the crankshaft of the engine is approximately 4 MPa to 13 Mpa.
Supposing that a fuel tank has become empty (the state of so-called “out of gas”) and the engine is to be started. In this state, air may have collected in a fuel pipe (delivery pipe) used for supplying the fuel to the two types of injectors. Therefore, at the time immediately after the start of fuel injection from each injector, the fuel cannot be injected normally in an “air purge period” which is a period until the air is purged from the fuel delivery pipe.
Japanese Patent Laying-Open No. 2006-207453 discloses a control device for an internal combustion engine including an in-cylinder injector and an intake manifold injector, for smoothing operation in the process of a change from an engine start period to normal operation, regardless of air collecting in the pipe. The control device is a control device for the internal combustion engine including a plurality of cylinders classified into a plurality of groups and including, for each cylinder, a first fuel injection mechanism for injecting fuel into a combustion chamber and a second fuel injection mechanism for injecting fuel into an intake manifold. The control device includes: a start period fuel injection control unit injecting fuel to each cylinder by selectively using only one of the first fuel injection mechanism and the second fuel injection mechanism in a start period of the internal combustion engine; a determination unit determining, at the start of the internal combustion engine; whether air has collected in each of first and second fuel supply systems for delivering fuel respectively to the first and second fuel injection mechanisms; a first fuel injection control unit injecting fuel to a part of the plurality of groups, using only one of the fuel injection mechanisms that is selected by the start period fuel injection control unit, in a predetermined period from the end of the start period in the case where the determination unit determines that air has collected, and a second fuel injection control unit injecting fuel to the remaining groups other than the part of the plurality of groups, with both of the first and second fuel injection mechanisms available, at a fuel injection ratio that is set based on a condition required for the internal combustion engine, in a predetermined period in the case where the determination unit determines that air has collected.
With the control device for the internal combustion engine, the fuel injection is controlled such that fuel is injected using only one of the fuel injection mechanisms (injectors) to each cylinder in the start period of the internal combustion engine. In the case where air may have collected in the fuel supply system, in the process of change from the end of the start period to the normal operation, start of fuel injection from the other fuel injection mechanism (injector) is not allowed for all cylinders simultaneously and is allowed for only a part of the cylinders. For the remaining cylinders, fuel injection using the one of the fuel injection mechanisms (injectors) that is used in the start period is continued. Therefore, even if fuel injection failure occurs due to influences of the accumulating air immediately after the use of the other fuel injection mechanism (injector) is started, reduction of the output of the whole internal combustion engine can be suppressed. As a result, a sudden decrease of the engine output can be prevented that is caused when the air is purged from the fuel supply system in the process of change from the start period (at the time of engine start or idling) to the normal operation, and accordingly the operating state can be made stable.
A feed pump provided at a fuel tank is used to supply fuel to a low-pressure-system delivery pipe for supplying fuel to the intake manifold injector and to a high-pressure-system delivery pipe for supplying fuel to the in-cylinder injector, and any one of the injectors (the injector of the low-pressure system for example) is opened (dummy injection) to purge air (here, the high-pressure fuel pump driven by the internal combustion engine is not driven at the time of the dummy injection). At this time, the air compressed in the other delivery pipe (the high-pressure-system delivery pipe which does not perform the dummy injection) expands until reaching normal pressure. The expanding air causes the fuel to be pushed out into the low-pressure fuel system communicating with the high-pressure fuel system. Therefore, from the low-pressure-system intake manifold injector from which air is to be purged, fuel could be emitted together with the air.
Japanese Patent Laying-Open No. 2006-207453, however, does not mention such fuel emission due to the dummy injection performed for discharging the collecting air.